Objective To investigate the expression of WNK1 and WNK4 genes in the mouse kidney. Methods The probes corresponding to the genes were amplified by RT PCR from mouse kidney, and then Northern blotting was performed on mouse multiple tissues membrane. The fragments were cloned into pGEM T vector,the correct plasmids were linearized and transcripted into RNA probes in vitro. In situ hybridization was performed on the mouse kidney sections. Results WNK1 gene was widely expressed in mouse tissues. There was a 9 5 kb strong signal in kidney. WNK4 gene was mainly expressed in kidney and had a 4 4 kb signal. In situ hybridization showed WNK1 gene was mostly expressed in the distal convoluted tubule whereas WNK4 gene was expressed in the medullary collecting ducts besides the distal convoluted tubules. Conclusion Both WNK1 and WNK4 genes were expressed in kidney. WNK4 was expressed more widely than WNK1 in mouse kidney.